Boiler Control Flashcards
What are the 2 most common types of boilers?
1) Fire tube boiler
2) Water tube boiler
What is the function of the deaerator?
To remove dissolved gasses from the BFW
What is the function of the mud drum?
Serves as a mineral and sediment trap
What does SAMA stand for?
Scientific and Apparatus Makers Association
What is the function of the steam drum?
Separation of BFW and steam
What is the function of the softeners?
To remove hard ions like Fe and replace them with softer ions like Na and K
What are 2 main boiler control objectives?
1) Increase availability based on supply/demand
2) Reduce flue gas emissions
What is the difference between a base loaded and a variable loaded boiler?
Base loaded boiler produces a fixed amount of steam while a variable loaded boiler is the one handling demand changes
What component does the plant master send it’s signal to?
Boiler master
After a boiler master receives a signal from a plant master it send a signal to ______________
Combustion control
What are the three kinds of combustion control?
1) Single point positioning/ Jackshaft control
2) Simple AFR control
3) Fully metered/ Cross limiting
What are the 2 issues with jackshaft control?
1) Purely mechanical system prone to failing
2) No flow measurements or control
Increasing FRD in a Simplified AFR Control causes the fuel to __________ the air into the burner which is a ____________.
Lead, safety issue
Decreasing FRD in a Simplified AFR Control causes the air to __________ the fuel out of the burner.
Lag
What is the biggest advantage of a Cross Limiting, Fully Metered combustio control system?
Fully imposed logic on a fully metered system ensures that air always leads the fuel into the burner when FRD increases by using selectors
What determines the optimum amount of Oxygen in a boiler?
1) Fuel type
2) Steam loading
What is swelling and when does it happen?
When drum pressure drops due to a high demand in the steam header, the water starts flashing into steam bubbles. This causes the level to read higher than what it actually is decreasing the BFW flow to the boiler. This is what’s called a swell.
What is shrink and when does it happen?
The drum pressure increases due to a decreased demand causing the steam bubbles to collapse. This causes the level to decrease momentarily which is opposite to the desired outcome. This is what’s called a shrink.
What is the most important CV for boiler SAFETY?
%O2 control
How can you minimize the shrink and swell effects in a boiler system?
Compensate for feedwater flow changes
While using a cross limiting, fully metered system you notice a decrease in pressure in the steam header line. What will this control system ensure happens in terms of fuel and air flow into the burner?
Fuel flow lags the air flow into the burner.
An operator is looking at a steam drum trend after a change in FRD and notices a sudden drop in level followed by a gradual ramp up, and a sudden increase in BFW flow followed by a gradual ramp down in the variable. What are the 2 effects that are happening?
Shrink and inverse response.
